Writing the .__str__()

00:00 I already built a minimal solution that has these two instance attributes and a small Car class in the last lesson. But now we’re going to add on the .__str__() method to print the output more nicely.

00:12 Define .__str__(). Again, it takes self as the parameter. And now we’re just going to return an f-string that I will make similar to what I did previously.

00:26 Maybe we’ll change it a bit, but some output like that looks pretty good. Only it’s not going to be blue_car, but here I need to reference generically to the instance itself.

00:38 So, f"The {self.color} car has {self.mileage} miles."

00:43 And so one thing you may have noticed is that the output here is kind of, like, stuck together. 20000 is a bit hard to read. And what I did earlier when putting in the number, I put this underscore in between here—that’s a valid way of writing an integer in Python.

00:58 You can use underscores in there. They’re going to get ignored. This is really just visually for you as a human or for other people reading your code to make it easier to understand what big numbers you’re working with.

01:10 But there’s also something similar for output. There’s something called the string mini-language. You can add it directly inside of an f-string by putting a colon and then you can put specific parameters to change how the variable gets printed.

01:28 In this case, I’m just going to put a comma here. And that means that Python is going to take whatever number is here and put commas in the appropriate places.

01:37 So it’s going to be every three digits. So it’s going to display as 20,000. And that’s these two little pieces of information. So the colon starts the string mini-syntax, and then the comma that says, “To an integer, every three digits, put a comma.”

01:53 All right, let’s try this out. I’ll press F5 and run it. And then let me create this blue_car again.

02:04 And now I should be able to just print(blue_car)

02:08 and I get this. Instead of __main__.Car object at memory address, I get The blue car has 20,000 miles. And you can see also the comma in here that separates three digits from two others.

02:20 That’s because of the colon comma that I put over here. All right, and I should create a second, a red_car. I’m going to say red_car = Car().

02:32 That is, it’s a Car that is "red", and it has 30_000 miles. And now I should be able to print(red_car) as well.

02:43 And I get the nice output. The red car has 30,000 miles. And that’s it. We solved the challenge. What’s the code that you came up with?